1. Field of the Invention
The present invention relates to a semiconductor test apparatus used in IC testing technology, and provides a power source to a measured device.
2. Description of the Related Art
FIG. 9 is a block diagrams showing the structure of the conventional technology for a semiconductor test apparatus. The DUT 9, which is the measured device, is mounted on the DUT (device under test) board 8 that is on the test head 16. By applying an arbitrary voltage to the DUT 9, a test of the DUT 9 is carried out. At a location separated from the test head 16, a control unit 15 is provided. On the control unit 15, switching power sources 1 and 2, control elements 6 and 7, and a control circuit 5 are provided in order to generate the arbitrary voltage. The switching power sources 1 and 2 generate a positive or negative constant voltage from each of the AC power sources S 12 and S 13 such that the sign of the applied voltage that is applied to the DUT 9 can be arbitrarily set, and forms circuits complementary to control elements 6 and 7.
Next, FIG. 10 shows the structure of the control circuit 5 of the semiconductor test device according to the conventional technology. A target setting voltage from a host computer (not illustrated) to the DUT 9 is supplied to a D/A conversion circuit 17 as a digital control signal CS 1. The D/A conversion circuit 17 converts the control signal CS 1 to an analog value, and outputs this to the calculating circuit 18.
In the calculating circuit 18, the difference between the analog control signal CS 1 output from the D/A conversion circuit 17 and the detected signal DS 1, which is the DUT terminal voltage of the DUT 9, is found and supplied to the bias generating circuit 19. At the bias generating circuit 19, a bias value for operating the control elements 6 and 7 is added to the differential signal output from the calculating circuit 18 and supplied to the control elements 6 and 7 respectively as control signals CS 2 and CS 3.
The voltage sources obtained by the control elements 6 and 7 are applied to the DUT 9 via the DUT board on the test head 16. The reason that the detected signal DS 1 is introduced from the DUT 9 rather than at the output terminals of the control elements 6 and 7 is to prevent a voltage setting error due to a voltage drop between the control elements 6 and 7 and the DUT 9.
However, in this conventional technology, there are the problems of a large loss due to the voltage drop of the control elements 6 and 7, heat generation, and efficiency. This is because in order to set the DUT 9 to an arbitrary voltage, a voltage supplying only the maximum voltage that can be set in the DUT 9 must be supplied to the control elements 6 and 7 from the switching power sources 1 and 2. Due to this, when the setting voltage of the DUT 9 is low, the voltage drop of the control elements 6 and 7 becomes large, and there are the problems concerning heat generation and efficiency.
In addition, due to the heat generation, not only is a heat radiating device necessary, but also high-density packaging becomes difficult, and thus miniaturization of the apparatus becomes difficult. Therefore, disposing the control elements 6 and 7 on the test head becomes a problem. Thus, due to making the distance between the control elements 6 and 7 large, there are the problems that deterioration of the frequency characteristics and noise superposition occur, and furthermore, energy loss and the like due to the voltage drop of the wiring part occurs.
In consideration of the problems described above, it an object of the present invention to provide a semiconductor test apparatus that allows reducing the consumed power, reduction of the amount of heat generated, an improvement of the frequency characteristics, and a reduction of noise superposition.
In a first aspect of the invention, a semiconductor test apparatus that applies a variable voltage to a measured device to test the measured device provides constant voltage generating devices that generate a plurality of variable voltages; voltage polarity control devices that control the polarity of the plurality of variable voltages generated by the constant voltage generating device; control elements that generate an applied variable voltage applied to the measured device from the plurality of variable voltages whose polarity is controlled by the voltage polarity control devices; a first control device that controls the generation operation of the applied variable voltage in the control elements based on the fixed applied voltage that is applied to the measured device and the terminal voltage of the measured device fed back from the measured device; and a second control device that controls the variable voltage value controlled by the constant voltage generating device and the polarity control controlled by the voltage polarity control device based on the fixed applied voltage that is applied to the measured device and the terminal voltage of the measured device fed back from the measured device. device based on the fixed applied voltage that is applied to the measured device and the terminal voltage of the measured device fed back from the measured device.
In a second aspect of the present invention, a semiconductor test apparatus according to the first aspect is characterized in that the second control device links the voltage drop amount of the control element to the fixed applied voltage that is applied to the measured device so that the value thereof becomes sufficient for the operation of the control elements, and controls the variable voltage value controlled by the constant voltage generating device and the polarity control controlled by the voltage polarity control device.
In a third aspect of the present invention, a semiconductor test apparatus according to the first aspect is characterized in that the control elements and the first control device are provided on the test head on which the measured device is mounted; a constant voltage generating device, the voltage polarity control device, and a second control device are provided on the control unit disposed separated from the test head; and a digital signal is used in signal propagation between the test head and the control unit.
In a fourth aspect of the present invention, a semiconductor test apparatus according to the first aspect is characterized in that the constant voltage generating device provides: a first switching constant voltage generating device that generates an output voltage that is larger than the fixed applied voltage that is applied to the measured device; and a second switching constant voltage generating device that generates an output voltage that is smaller than the fixed applied voltage that is applied to the measured device.
In a fifth aspect of the present invention, a semiconductor test apparatus according to the first aspect is characterized in that the voltage polarity control device can reverse or not reverse the polarity of the plurality of variable voltages generated by the constant voltage generating device or short the plurality of variable voltages based on the control of the second control device.
In a sixth aspect of the present invention, a semiconductor test apparatus according to the second aspect is characterized in that the second control device: A: in the case that the fixed applied voltage that is applied to the measured device is positive, the voltage output of the first switching constant voltage generating device is output as is in the case that the output voltage of the first switching constant voltage generating device can be set to a voltage equivalent to the fixed applied voltage having added thereto the amount of voltage drop necessary for allowing the control element to operate stably; the minimum output voltage of the first switching constant voltage generating device is output in the case that a voltage equivalent to the fixed applied voltage having added thereto the amount of voltage drop necessary for allowing the control element to operate stably is lower than the minimum output voltage of the first switching constant voltage generating device; the output voltage of the second switching voltage generating device is output as is in the case that the output voltage of the second switching constant voltage generating device can be set to a voltage equivalent to the fixed applied voltage having subtracted therefrom the amount of voltage drop necessary for allowing the control element to operate stably; the output of the second switching constant voltage generating device is shorted by the voltage polarity control device in the case that a voltage equivalent to the fixed applied voltage having subtracted therefrom the amount of voltage drop necessary for allowing the control element to operate stably is positive, and this voltage is smaller than the minimum output voltage of the second switching constant voltage generating device; the minimum output voltage of the second switching constant voltage generating device is output and the output of the voltage polarity control device located at the output side of the second switching constant voltage generating device is reversed in the case that a voltage equivalent to the fixed applied voltage having subtracted therefrom the amount of voltage drop necessary for allowing the control element to operate stably is negative, and this voltage is smaller than the minimum output voltage of the second switching constant voltage generating device; the variable voltage value controlled by the constant voltage generating device and the polarity control controlled by the voltage polarity control device are controlled such that the absolute value of the output voltage from the second switching constant voltage generating device is output and the output of the voltage polarity control device that is located at the output side of the second switching constant voltage generating device is reversed in the case that a voltage equivalent to the fixed applied voltage having subtracted therefrom the amount of voltage drop necessary for allowing the control element to operate stably is negative and larger than the minimum output voltage of the second switching voltage generating device; and B: in the case that the target voltage applied to the measured device is negative: the output voltage of the second switching constant voltage generating device is output and the output of the voltage polarity control device, which is located at the output side of the second switching constant voltage generating device, is reversed in the case that the output voltage of the second switching constant voltage generating device can be set to the absolute value of a voltage equivalent to the fixed applied voltage having subtracted therefrom the amount of voltage drop necessary for allowing the control element to operate stably; the minimum output voltage of the second switching constant voltage generating device is output and the output of the voltage polarity control device, which is located at the output side of the second switching constant voltage generating device is reversed in the case that the absolute value of the a voltage equivalent to the fixed applied voltage having subtracted therefrom the amount of voltage drop necessary for allowing the control element to operate stably is lower than the minimum output voltage of the second switching constant voltage generating device; the output voltage of the first switching constant voltage generating device is output and the output of the voltage polarity control device, which is located at the output side of the second switching constant voltage generating device, is reversed in the case that the output voltage of the first switching constant voltage generating device can be set to the absolute value of a voltage equivalent to the fixed applied voltage having added thereto the amount of voltage drop necessary for allowing the control element to operate stably; the output of the voltage polarity control device, which is located at the output side of the first switching constant voltage generating device, is shorted in the case that a voltage equivalent to the fixed applied voltage having added thereto the amount of voltage drop necessary for allowing the control element to operate stably is negative and smaller than the value produced by multiplying the minimum output voltage of the first switching constant voltage generating device by xe2x88x921; the minimum output voltage of the first switching constant voltage generating device is output in the case that a voltage equivalent to the fixed applied voltage having added thereto the amount of voltage drop necessary for allowing the control element to operate stably is positive and smaller than the minimum output voltage of the first switching constant voltage generating device; and the variable voltage value controlled by the constant voltage generating device and the polarity control controlled by the voltage polarity control device are controlled such that the output voltage of the first switching constant voltage generating device is output as is in the case that a voltage equivalent to the fixed applied voltage having added thereto the amount of voltage drop necessary for allowing the control element to operate stably is positive and larger than the minimum output voltage of the first switching constant voltage generating device.
In a seventh aspect of the present invention, a semiconductor test apparatus according to the first aspect is characterized in that the control elements and the first control device form one group, the groups are provided in plurality in parallel, and the plurality of applied variable voltages generated by each of the groups is applied to the measured device.